Chan H C, Sun K Q, Magin R L, Swartz H M
Department of Electrical and Computer Engineering, University of Illinois, Champaign--Urbana 61801.
Bioconjug Chem. 1990 Jan-Feb;1(1):32-6. doi: 10.1021/bc00001a004.
The biological and physical properties of albumin and nitroxides make them attractive candidates as special purpose MRI contrast agents which could be used to study the intravascular compartment or specific targets in tissues. In this study, albumin-nitroxide complexes were prepared by reduction and alkylation of the disulfide bonds of the protein and characterized by electron spin resonance and ultraviolet absorption spectroscopy. An average of six nitroxides were bound covalently to each molecule of human serum albumin. The water proton relaxivity of the protein-bound nitroxide (at 20 MHz and 37 degrees C) was 4-fold greater than that of the free nitroxide. The digestion of the nitroxide-albumin complexes by cells or by trypsin decreased the relaxivity of the nitroxide-protein complex. The rate of reduction of albumin-bound nitroxide by cells was much slower than that of the free nitroxide but still was oxygen-sensitive (2-3-fold increase in the rate of reduction in the absence of oxygen).
白蛋白和氮氧化物的生物学和物理特性使其成为极具吸引力的特殊用途磁共振成像（MRI）造影剂候选物，可用于研究血管内区域或组织中的特定靶点。在本研究中，通过还原和烷基化蛋白质的二硫键制备了白蛋白-氮氧化物复合物，并通过电子自旋共振和紫外吸收光谱对其进行了表征。平均每个分子的人血清白蛋白共价结合六个氮氧化物。与蛋白质结合的氮氧化物的水质子弛豫率（在20 MHz和37摄氏度下）比游离氮氧化物高4倍。细胞或胰蛋白酶对氮氧化物-白蛋白复合物的消化降低了氮氧化物-蛋白质复合物的弛豫率。细胞对与白蛋白结合的氮氧化物的还原速率比游离氮氧化物慢得多，但仍然对氧气敏感（在无氧条件下还原速率增加2至3倍）。
